macros: Move test for NEVER interest to callsite

This lets us completely skip `Span::new` in this case. This brings the benchmarks for the disabled case back into parity with `log`. Before: ``` Running target/release/deps/no_subscriber-1064195d321c8640 running 5 tests test bench_1_atomic_load ... bench: 0 ns/iter (+/- 0) test bench_costly_field_no_subscriber ... bench: 6 ns/iter (+/- 0) test bench_log_no_logger ... bench: 0 ns/iter (+/- 0) test bench_no_span_no_subscriber ... bench: 0 ns/iter (+/- 0) test bench_span_no_subscriber ... bench: 6 ns/iter (+/- 0) test result: ok. 0 passed; 0 failed; 0 ignored; 5 measured; 0 filtered out Running target/release/deps/subscriber-7319775649c47f41 running 4 tests test span_no_fields ... bench: 37 ns/iter (+/- 10) test span_repeatedly ... bench: 5,626 ns/iter (+/- 812) test span_with_fields ... bench: 101 ns/iter (+/- 20) test span_with_fields_record ... bench: 1,035 ns/iter (+/- 171) test result: ok. 0 passed; 0 failed; 0 ignored; 4 measured; 0 filtered out ``` After: ``` Running target/release/deps/no_subscriber-1064195d321c8640 running 5 tests test bench_1_atomic_load ... bench: 0 ns/iter (+/- 0) test bench_costly_field_no_subscriber ... bench: 0 ns/iter (+/- 0) test bench_log_no_logger ... bench: 0 ns/iter (+/- 0) test bench_no_span_no_subscriber ... bench: 0 ns/iter (+/- 0) test bench_span_no_subscriber ... bench: 0 ns/iter (+/- 0) test result: ok. 0 passed; 0 failed; 0 ignored; 5 measured; 0 filtered out Running target/release/deps/subscriber-7319775649c47f41 running 4 tests test span_no_fields ... bench: 36 ns/iter (+/- 8) test span_repeatedly ... bench: 5,381 ns/iter (+/- 1,075) test span_with_fields ... bench: 110 ns/iter (+/- 19) test span_with_fields_record ... bench: 1,019 ns/iter (+/- 247) test result: ok. 0 passed; 0 failed; 0 ignored; 4 measured; 0 filtered out ``` Signed-off-by: Eliza Weisman <eliza@buoyant.io>
tokio-rs · Jan 18, 2019 · bdeea40 · bdeea40
1 parent f0170be
commit bdeea40
Showing 1 changed file with 37 additions and 27 deletions.
diff --git a/tokio-trace/src/lib.rs b/tokio-trace/src/lib.rs
@@ -448,20 +448,25 @@ macro_rules! span {
             use $crate::{callsite, field::{Value, AsField}, Span};
             use $crate::callsite::Callsite;
             let callsite = callsite! { span: $name, $( $k ),* };
-            let mut span = Span::new(callsite.interest(), callsite.metadata());
-            // Depending on how many fields are generated, this may or may
-            // not actually be used, but it doesn't make sense to repeat it.
-            #[allow(unused_variables, unused_mut)] {
-                if !span.is_disabled() {
-                    let mut keys = callsite.metadata().fields().into_iter();
-                    $(
-                        let key = keys.next()
-                            .expect(concat!("metadata should define a key for '", stringify!($k), "'"));
-                        span!(@ record: span, $k, &key, $($val)*);
-                    )*
-                };
+            let interest = callsite.interest();
+            if interest.is_never() {
+                Span::new_disabled()
+            } else {
+                let mut span = Span::new(interest, callsite.metadata());
+                // Depending on how many fields are generated, this may or may
+                // not actually be used, but it doesn't make sense to repeat it.
+                #[allow(unused_variables, unused_mut)] {
+                    if !span.is_disabled() {
+                        let mut keys = callsite.metadata().fields().into_iter();
+                        $(
+                            let key = keys.next()
+                                .expect(concat!("metadata should define a key for '", stringify!($k), "'"));
+                            span!(@ record: span, $k, &key, $($val)*);
+                        )*
+                    };
+                }
+                span
             }
-            span
         }
     };
     (@ record: $span:expr, $k:expr, $i:expr, $val:expr) => (
@@ -540,22 +545,27 @@ macro_rules! event {
                 target:
                 $target, $( $k ),*
             };
-            let mut event = Event::new(callsite.interest(), callsite.metadata());
-            // Depending on how many fields are generated, this may or may
-            // not actually be used, but it doesn't make sense to repeat it.
-            #[allow(unused_variables, unused_mut)] {
-                if !event.is_disabled() {
-                    let mut keys = callsite.metadata().fields().into_iter();
-                    let msg_key = keys.next()
-                        .expect("event metadata should define a key for the message");
-                    $(
-                        let key = keys.next()
-                            .expect(concat!("metadata should define a key for '", stringify!($k), "'"));
-                        event!(@ record: event, $k, &key, $($val)*);
-                    )*
+            let interest = callsite.interest();
+            if interest.is_never() {
+                Event::new_disabled()
+            } else {
+                let mut event = Event::new(callsite.interest(), callsite.metadata());
+                // Depending on how many fields are generated, this may or may
+                // not actually be used, but it doesn't make sense to repeat it.
+                #[allow(unused_variables, unused_mut)] {
+                    if !event.is_disabled() {
+                        let mut keys = callsite.metadata().fields().into_iter();
+                        let msg_key = keys.next()
+                            .expect("event metadata should define a key for the message");
+                        $(
+                            let key = keys.next()
+                                .expect(concat!("metadata should define a key for '", stringify!($k), "'"));
+                            event!(@ record: event, $k, &key, $($val)*);
+                        )*
+                    }
                 }
+                event
             }
-            event
         }
     });
     (target: $target:expr, $lvl:expr, $($arg:tt)+ ) => (